Mulching containers with marble chips?

gosalskJune 10, 2014

I have some bromeliads in containers that keep getting blown over. Already they are in terra cotta pots that are already probably too big for them. I have some marble chips and am considering using them as a mulch to further weight the pots down.

My concern is that bromeliads tend to like slightly acidic soil and I don't want to alter it too much. Just how much do marble chips alter the ph of the medium?

It's already acidic, I would think; it's pine bark, peat, and perlite mixed together at about a 3-1-1 ratio.

I also grow plants in windy conditions, which is one reason I substitute granite for perlite in my 5-1-1 mix. The granite adds considerable weight to the plastic containers I use and they don't blow over even in fairly strong winds.

I've never used marble chips in my containers so I cannot say what they might do. A quick Google search indicates that marble may increase soil pH. Exactly how much I cannot say but you can always do some research. Google is your friend.

You might want to consider adding a bit of pea gravel to the top of one container as a test. In my area, pea gravel is very cheap. How much it would change your soil pH and the water drainage, if at all, I don't know, but it might be a bit better than using marble chips. One of the gardening books I have suggests using a thin layer of pea gravel as a top dressing when growing plants from seeds in containers. Based on that I'm guessing pea gravel wouldn't radically change the soil chemistry.

I appreciate the reply. I did try to research it, but mostly all I found was vague cautions. Where do you get pebble-sized granite? I think that would be great to mix in with the dirt instead of perlite.

I want to use marble chips because I happen to have several bags left over from a project, just sitting around. Obviously the cost is minimal no matter what I use, so I probably shouldn't bother with the marble. But the more I think about it, the less I think it's a big deal. Bromeliads typically only live 3-4 years and the other ingredients in the soil are so acidic -- I doubt it could hurt anything since marble lasts a long time in the landscape. How much could it leach out given how much lime it takes to sweeten soil?

I did make sure to wash the marble before putting it in, as out of the bag it's covered by marble powder, which I imagine would be distributed to the soil really quickly.

When I mentioned the possibility of using pea gravel, about 1/4" to1/2" in size, as a top dressing for your containers I was referring to regular pea stone that you can get at any landscape supply or big box store.

Usually granite typically can be found at a feed store.

I didnt have a chance to research marble use in soils but noticed the same thing you did, mostly warnings and cautions that marble will raise soil pH. If you have a lot of marble to use, and if you wish to experiment on a couple of your containers, then I say try it as a top dressing. That's the only way you will know if it works or not, or if it bothers your plants. Just don't try it on any valuable or important plants until you know whether it works or not.

Yes, the crushed granite can be found at any feed store for the most part. Gran-I-Grit is one of the more popular brands. I get mine from Agway... not sure of your location, so I don't know if there are any nearby you.
I use the "grower" size as opposed to the "starter".

I used white marble rocks to mulch most of my plants for several years now, and it hasn't effected any of them in the slightest. I originally did this because I have a cute little stray cat that adopted me and lives in my backyard. When I moved my plants outside after winter, he thought the large pots made perfect places to tinkle, HaHa. So I covered all of them in a layer of white marble rocks, which worked out great and looks nice, too. In fact, I was going to go buy another bag, to layer off the rest of my plants with them as well. Because it bugs me having most pots covered with them and a few that are not. Plus it'll sort of gives them all a similar look, since I use the same type of pot (of different sizes) for just about all of my plants. The marble rocks don't seem to have any adverse effects. Just rinse the marble dust off of them first.